1. Field of the Invention
The invention relates generally to monomers and conjugated polymers, and their use in electronic devices.
2. Description of the Related Art
The use of organic light-emitting displays is increasing as a replacement for liquid crystal displays (LCD) in many applications. Patents and articles address ways to maximize the quantum efficiency of the organic light-emitting diodes (OLEDs) as well as change the color of the light emitted from organic light-emitting diodes (OLEDs).
Equalizing the amount of carriers injected from the cathode and anode can increase the quantum efficiency of the light-emitting diode (LED) device. Carrier injection is sensitive to the height of the energy barriers at the interface between an electrode and the polymer in an organic LED. In the past, the highest occupied molecular orbital (HOMO) or lowest unoccupied molecular orbital (LUMO), have been tuned to increase efficiency and/or change color.
In U.S. Provisional Patent Application No. 60/384,494, which is assigned to the current assignee hereof and incorporated herein by reference, discloses a new class of polymer with tunable energy levels. This earlier approach offers the opportunity to match the LUMO of the polymer with the work function of the material of the cathode.
Controlling the energy level of the polymer so that the HOMO matches the work function of the anode and the LUMO matches the work function of the cathode without changing the emission color can be a challenge. This is especially true for blue light emitting polymers.